Cannot connect my new Nighthawk

I cannot get my new extender connected to the router. In the frst place, the extender appeared as a possible network, but could not get it connected by the VPS. When pushing the VPS button the lights should turn red until connected. They where just white, and the extender showed as a network option, but with "no internet connection". After a couple of new trials, the extender is not visible any longer on the PC.  Having pushed the "reset to factory settings" makes no difference.